Field of Endeavor
The present disclosure relates to a fitting assembly, and more particularly, to a coupling nut assembly for coupling annular fittings.
Brief Description of the Related Art
A coupling nut is commonly used to connect annular fittings for establishing a connection between two equipment ports, such as between a fill valve of a tank and an inlet/outlet water port. More often than not, typical use of the coupling nut may be evident in relation to plumbing connection between the fill valve shank of the tank, such as a toilet tank, and an inlet/outlet water port for supplying/draining water. A bottom portion of the fill valve shank of the toilet tank is connected to the inlet port of a water pipe via plastic or stainless braided hose by utilizing the coupling nut. For such coupling, or when required decoupling, the coupling nut generally requires a hand tightening or loosening operation thereon. For enabling such tightening and loosening, threads are incorporated over mating surfaces of coaxial flanged connector components of the coupling nut. An outer coaxial connector component is rotated against an inner coaxial connector component through the threads for tightening and loosening the coupling nut to couple or decouple the water pipe with the fill valve shank. The coupling nut usually fails if subjected to over-tightening. The over-tightening of the coupling nut is more common in case of machine tightening of the coupling nut. To address the issue of application of over-tightening, several attempts in the past have been made. For instance, generally, conventional coupling nuts are hexagonal-shaped that prompts users for machine tightening, such as to use wrenches to tighten thereto, so the various attempts have been made to change the shapes of such coupling nut that do not prompt the use of wrenches for tightening thereto.
In an another attempt, manuals for installation of the coupling nut clearly have been modified to include recommended use of hand tightening and loosening operations to be performed on the coupling nut to avoid premature breakage of the coupling nut due to over-tightening. A typical coupling nut ‘N’ with such an instruction and breakage due to over-tightening may be evident in FIGS. 11A to 11E. Particularly FIG. 11A illustrates the coupling nut ‘N’ assembled with the annular fittings, and FIGS. 11B to 11E illustrate breakage thereof due to over-tightening.
However, hand tightening of the coupling nut may even not be able to preclude over-tightening of the coupling nut completely due to the inherent configuration of the threads formed in the coupling nut, more particularly, the configuration of the threads at along a bottom portion of an inner circumference side of the one of coaxial connector component. A typical inner coaxial connector component ‘C’ may be evident in FIGS. 12 and 13A to 13C. The coaxial connector component ‘C’ along the inner circumference side ‘I’ includes threads ‘T,’ that results connection of the coaxial connector components ‘C’ with the annular fittings. Further, the threads ‘T’ also extend towards a bottom portion ‘B’ (mentioned as ‘Bottom Thread Region’ ‘T1’) along the inner circumference side ‘I’ of the coaxial connector component ‘C.’ Such ‘Bottom Thread Region’ ‘T1’ is such that it may provoke additional rotation of the coupling nut than what is generally required. Such additional rotation or say over-tightening of the coupling nut may increase tensile stresses on a first thread of the ‘Bottom Thread Region’ ‘T1’, as indicated by arrow. Further, a compression seal ‘S,’ (see FIG. 13A) a component of the coupling nut ‘N’ that is disposed between the annular fittings also applies an opposite tensile stress of the tensile stress due to the thread tightening (as indicated by arrow), in turn developing higher stress in a bottom flanged region ‘F’ of the coupling nut, as indicated by a horizontal line ‘H’ in FIG. 13A, thereby resulting in failure of the nut. FIGS. 13A to 13C illustrated herein depict such tensile stress in the bottom flanged region ‘F.’ Specifically, FIG. 13B illustrates stress transfer mechanism on the bottom flange region resulting fracture. Further, FIG. 13C illustrates a stress profile of the conventional coupling nut housing.
Such tensile stress results failure of the coupling nut, which may in-turn cause leakage or flooding. The coupling nut may fail instantly or may fail subsequently due to creep. Since the data on how the coupling nut modulus changes when subjected to constant stress may not be generally available, it may become even harder to predict when subsequent failure of the coupling would take place, thereby resulting in unexpected leakage or flooding.
While the previously known coupling nuts may have generally been considered satisfactory for their intended purposes, there has remained a need in the art for a coupling nut that can be improved to be substantially more manageable in terms of avoiding over-tightening and resultant fracture to avoid unexpected or potential leakage or flooding.